Forums
Bruker Media
Community Media
Bruker AFM Probes
SPM Digest
Application Notes
NanoTheater
Website
中文
Brochures & Datasheets
Publications
Probes Catalog
Events
Manuals & Documentation
Presentations
Guide to AFM Modes
News
Journal Club
Webinars & Video
Nanovations
Other
Q1. I tried to measure friction force by doing lateral scan. While scanning on my sample (a), retrace line on monitor showed there was a part that friction value was over 10V.
However, after scanning was finished, I got a different friction value on the same spot (b).
What am I did wrong? How do I interpret (b) images to get reasonable friction data?
Q2. From paper, calculating friction force in newton units from measured voltage, vertical sensitivity is required.
From nanoscope 7.3 which I used for my measurement, while I tried to get vertical sensitivity, it changed its value every time.
I might did something not properly, so could you tell the correct procedure to get right value?
Q3. I tried to image end of AFM probe with Silicon Nitride tip, but could not succeed it.
Does it need some specific AFM probe to image the tip end?
Q4. While doing contact mode, does AFM always gives same normal load to scanning surface?
Q5. From nanoscope 7.3, is it possible to control the AFM tip motion in contact mode?
I tried to avoid scratching my sample surface back and forth, but could not find any detail control from program and also from manual.
(Yes I want to scratch sample with one direction)
If possible can someone from Bruker email me the answers on seong.8@osu.edu ?
Thank You in advance.
Hello Hikari81
Q1 - In (a), you are looking a the blue line to measure 10V, which is the trace direction (left to right scan). However, you are collecting the data in the retrace direction (right to left) for the saved image. The frictional contrast will be due to the lateral bending of the cantilever, which will be in opposite directions for the trace and retrace directions. Also, you only save one scan direction to create a scan, and you have choosed the Retrace direction to save the scan. So, if you look at the red line in the realtime display (retrace), then this is the data that is being collected for the saved image (b). Often operators conducting FFM (or LFM) will collect both the trace and retrace scan direction as two seperate Friction images in order to compare the trace and retrace scan directions.
Q2 - To get the vertical sensitivity, you would collect a force curve on a hard material which will not deform under the probe. This may mean that you need put in a different sample from FFM sample in order to collect this force curve. A sapphire sample is often used for stiffer cantilevers. For the lower spring constant silicon nitride cantilevers often used for contact mode and FFM, you could use a glass slide or calibration grid. Once you have the force curve, you determine deflection sensitivity by determing the slope of the contact portion of the force curve using the software. Reasons that this sensitivity could be changing could either be using a sample which is deforming under the probe, or a dirty tip. Also, once you determine deflection sensitivity, you cannot readjust the laser position on the cantilever since that will cause this value to change as well. On another note, often people that you trying to determine friction force in Newtons will want to determine the lateral or torsional sensitivity. If you are interested in this, I can send you some info on that as well.
Q3 - How are you trying to image the end of the silicon nitride probe? If you are just turning the cantilever substrate upside down and trying to land on top of the cantilever, then you are probably bending the cantilever backward since now your sample is a soft spring (low spring constant cantilever). You would likely have more luck in TappingMode in this case than contact mode. Another way to do this would be to break the cantilever off the substrate and mount the cantilever on some adhesive material and image it in Tapping. Of course, you would do this at the end of the experiment since you could not use the tip again after this. If you want to give me more details about the problems that you are having, I can try to help you further here.
Q4 - In contact mode, you adjust the amount of imaging force applied by adjusting the Deflection Setpoint parameter. Usually, you will want this at a level which is low enough that does not apply more force than necessary, but high enough to still image the sample well. I will usually do this by decreasing the setpoint after engagement until I find where the tip pulls off the sample, and then begin increasing the setpoint until it comes back onto the sample. You can also do this by using the force curve as a guide as well, which is described in the manual.
Q5 - You would avoid scratching the sample by adjust the force to a minimum with the Deflection Setpoint, as descibed in Q4. If you want to create scratches, there are different was to do this depending on what instrument that you have. Can you tell me what model instrument that you are running? (MultiMode, Dimension, Nanoman, ...).
You are also welcome to email me at my Bruker address at john.thornton@bruker-nano.com if I can help you further.
Thanks,John
Thank you John.
By the way, can you check you email? I sent additional questions to your email to get more help.
That would be really nice if you can help me.
Thank you.